1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/cred.h>
3 #include <linux/init.h>
4 #include <linux/kernel.h>
5 #include <linux/quotaops.h>
6 #include <linux/sched.h>
7 #include <linux/slab.h>
8 #include <net/netlink.h>
9 #include <net/genetlink.h>
10
11 static const struct genl_multicast_group quota_mcgrps[] = {
12 { .name = "events", },
13 };
14
15 /* Netlink family structure for quota */
16 static struct genl_family quota_genl_family __ro_after_init = {
17 .module = THIS_MODULE,
18 .hdrsize = 0,
19 .name = "VFS_DQUOT",
20 .version = 1,
21 .maxattr = QUOTA_NL_A_MAX,
22 .mcgrps = quota_mcgrps,
23 .n_mcgrps = ARRAY_SIZE(quota_mcgrps),
24 };
25
26 /**
27 * quota_send_warning - Send warning to userspace about exceeded quota
28 * @qid: The kernel internal quota identifier.
29 * @dev: The device on which the fs is mounted (sb->s_dev)
30 * @warntype: The type of the warning: QUOTA_NL_...
31 *
32 * This can be used by filesystems (including those which don't use
33 * dquot) to send a message to userspace relating to quota limits.
34 *
35 */
36
37 void quota_send_warning(struct kqid qid, dev_t dev,
38 const char warntype)
39 {
40 static atomic_t seq;
41 struct sk_buff *skb;
42 void *msg_head;
43 int ret;
44 int msg_size = 4 * nla_total_size(sizeof(u32)) +
45 2 * nla_total_size_64bit(sizeof(u64));
46
47 /* We have to allocate using GFP_NOFS as we are called from a
48 * filesystem performing write and thus further recursion into
49 * the fs to free some data could cause deadlocks. */
50 skb = genlmsg_new(msg_size, GFP_NOFS);
51 if (!skb) {
52 printk(KERN_ERR
53 "VFS: Not enough memory to send quota warning.\n");
54 return;
55 }
56 msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
57 "a_genl_family, 0, QUOTA_NL_C_WARNING);
58 if (!msg_head) {
59 printk(KERN_ERR
60 "VFS: Cannot store netlink header in quota warning.\n");
61 goto err_out;
62 }
63 ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
64 if (ret)
65 goto attr_err_out;
66 ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID,
67 from_kqid_munged(&init_user_ns, qid),
68 QUOTA_NL_A_PAD);
69 if (ret)
70 goto attr_err_out;
71 ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
72 if (ret)
73 goto attr_err_out;
74 ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
75 if (ret)
76 goto attr_err_out;
77 ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
78 if (ret)
79 goto attr_err_out;
80 ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID,
81 from_kuid_munged(&init_user_ns, current_uid()),
82 QUOTA_NL_A_PAD);
83 if (ret)
84 goto attr_err_out;
85 genlmsg_end(skb, msg_head);
86
87 genlmsg_multicast("a_genl_family, skb, 0, 0, GFP_NOFS);
88 return;
89 attr_err_out:
90 printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
91 err_out:
92 kfree_skb(skb);
93 }
94 EXPORT_SYMBOL(quota_send_warning);
95
96 static int __init quota_init(void)
97 {
98 if (genl_register_family("a_genl_family) != 0)
99 printk(KERN_ERR
100 "VFS: Failed to create quota netlink interface.\n");
101 return 0;
102 };
103 fs_initcall(quota_init);
104
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